libcurl第八课 下载Http或FTP图片

场景一 保存成图片
代码
static size_t WriteFile(void *ptr, size_t size, size_t nmemb, void *stream)
{
std::ofstream* ofs = (std::ofstream*)stream;
size_t nLen = size * nmemb;
ofs->write((char*)ptr, nLen);
return nLen;
}
static void TestStorePhotoFileFromUrl()
{
std::ofstream ofs;
ofs.open("aa3ab705-a7d5-4892-b63d-2ccdb54db9a21561977015816.jpg", std::ios::out | std::ios::binary);
std::string strUrl = "ftp://192.168.11.161:9010/successImage/aa3ab705-a7d5-4892-b63d-2ccdb54db9a21561977015816.jpg";
std::string strPhotoBuffer;
CURL *pCurlHandle;
pCurlHandle = curl_easy_init();
curl_easy_setopt(pCurlHandle, CURLOPT_URL, strUrl.c_str());
curl_easy_setopt(pCurlHandle, CURLOPT_WRITEDATA, &ofs);
curl_easy_setopt(pCurlHandle, CURLOPT_WRITEFUNCTION, WriteFile);
CURLcode nCurlRet = curl_easy_perform(pCurlHandle);
if ((nCurlRet != CURLE_OK) && (nCurlRet != CURLE_WRITE_ERROR))
{
std::cout << "通过LibCurl获取:" << strUrl << "图片失败，错误码是:" << nCurlRet;
}
ofs.close();
curl_easy_cleanup(pCurlHandle);
}

场景二 保存到缓存
代码
static size_t WriteBuffer(void *ptr, size_t size, size_t nmemb, void *stream)
{
std::string* pStrBuffer = (std::string*)stream;
size_t nLen = size * nmemb;
pStrBuffer->append((char*)ptr, nLen);
return nLen;
}
static void TestStoreBufferFromUrl()
{
std::string strUrl = "ftp://192.168.11.161:9010/successImage/aa3ab705-a7d5-4892-b63d-2ccdb54db9a21561977015816.jpg";
std::string strPhotoBuffer;
CURL *pCurlHandle;
pCurlHandle = curl_easy_init();
curl_easy_setopt(pCurlHandle, CURLOPT_URL, strUrl.c_str());
curl_easy_setopt(pCurlHandle, CURLOPT_WRITEDATA, &strPhotoBuffer);
curl_easy_setopt(pCurlHandle, CURLOPT_WRITEFUNCTION, WriteBuffer);
CURLcode nCurlRet = curl_easy_perform(pCurlHandle);
if ((nCurlRet != CURLE_OK) && (nCurlRet != CURLE_WRITE_ERROR))
{
std::cout << "通过LibCurl获取:" << strUrl << "图片失败，错误码是:" << nCurlRet;
}
else
{
std::ofstream ofs;
ofs.open("aa3ab705-a7d5-4892-b63d-2ccdb54db9a21561977015816.jpg", std::ios::out | std::ios::binary);
ofs << strPhotoBuffer;
ofs.close();
}
curl_easy_cleanup(pCurlHandle);
}

注意：
std::ios::binary必须携带，否则图片写文件有丢失